| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Hartman, Henrik, et al.
(författare)
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Negative ion relaxation and reactions in a cryogenic storage ring
- 2020
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Ingår i: Journal of Physics: Conference Series Vol 1412. - : IOP Publishing. - 1742-6588 .- 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- An overview of recent experimental results of studies of negative atomic and molecular ions in the Double ElectroStatic Ion-Ring ExpEriment, DESIREE is given. Metastable level lifetimes in atomic negative ions have been measured by time-dependent laser photodetachment. Rotational relaxation of diatomic anions is studied by near-threshold photodetachment. Spontaneous decays of small metal cluster anions by electron emission and fragmentation is studied with decay-channel specificity. Finally, mutual neutralisation of pairs of negative and positive ions has been investigated with initial and final state selectivity.
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| 3. |
- Seitz, Fabian, et al.
(författare)
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Ions colliding with clusters of fullerenes-Decay pathways and covalent bond formations
- 2013
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 139:3
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental results for the ionization and fragmentation of weakly bound van der Waals clusters of n C-60 molecules following collisions with Ar2+, He2+, and Xe20+ at laboratory kinetic energies of 13 keV, 22.5 keV, and 300 keV, respectively. Intact singly charged C-60 monomers are the dominant reaction products in all three cases and this is accounted for by means of Monte Carlo calculations of energy transfer processes and a simple Arrhenius-type [C-60](n)(+) -> C-60(+) + (n - 1)C-60 evaporation model. Excitation energies in the range of only similar to 0.7 eV per C-60 molecule in a [C-60](13)(+) cluster are sufficient for complete evaporation and such low energies correspond to ion trajectories far outside the clusters. Still we observe singly and even doubly charged intact cluster ions which stem from even more distant collisions. For penetrating collisions the clusters become multiply charged and some of the individual molecules may be promptly fragmented in direct knock-out processes leading to efficient formations of new covalent systems. For Ar2+ and He2+ collisions, we observe very efficient C-119(+) and C-118(+) formation and molecular dynamics simulations suggest that they are covalent dumb-bell systems due to bonding between C-59(+) or C-58(+) and C-60 during cluster fragmentation. In the Ar2+ case, it is possible to form even smaller C-120-2m(+) molecules (m = 2-7), while no molecular fusion reactions are observed for the present Xe20+ collisions.
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| 4. |
- Stockett, M.H., et al.
(författare)
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Spontaneous decay of small copper cluster anions, Cu_N^-, N = 3 - 6
- 2015
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Ingår i: Journal of Physics, Conference Series. - 1742-6588 .- 1742-6596. ; 635
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We have measured the spontaneous neutral particle emission from beams of copper cluster anions (Cu_N, N = 3 to 6) stored in an electrostatic storage ring. These experiments have show that multiple structural isomers may be present in the beam.
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| 5. |
- Zettergren, Henning, et al.
(författare)
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Bond formation in C-59(+)-C-60 collisions
- 2014
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Ingår i: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- In this work, we show that keV-ions are able to remove single carbon atoms from individual fullerenes in clusters of C-60 molecules. This very efficiently leads to the formation of exotic q dumbbell molecules through secondary C-59(+) - C-60 collisions within the fragmenting cluster. Such molecular fusion processes are inherently different from those induced by photons where only products with even numbers of carbon atoms are observed. Thus, ion collisions ignite unique and hitherto overlooked secondary reactions in small aggregates of matter. This relates to the question on how complex molecules may form in e.g. space.
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| 6. |
- Zettergren, Henning, et al.
(författare)
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Formation of dumb-bell C118 and C119 inside clusters of C60 -molecules
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Tidskriftsartikel (refereegranskat)abstract
- We report highly selective covalent bond-modifications in collisions between keV alpha particles and van der Waals clusters of C60-fullerenes. Surprisingly, C119+ and C118+ are the dominant molecular fusion products. We use Molecular Dynamics simulations to show that C59+ and C58+ ions - effectively produced in prompt knock-out processes with He2+ - react rapidly with C60 to form dumb-bell C119+ and C118+ . Ion impact on molecular clusters in general is expected to lead to efficient secondary reactions of interest for astrophysics. These reactions are different from those induced by photons.
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| 7. |
- Zettergren, Henning, et al.
(författare)
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Formations of Dumbbell C-118 and C-119 inside Clusters of C-60 Molecules by Collision with alpha Particles
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:18
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Tidskriftsartikel (refereegranskat)abstract
- We report highly selective covalent bond modifications in collisions between keV alpha particles and van der Waals clusters of C-60 fullerenes. Surprisingly, C-119(+) and C-118(+) are the dominant molecular fusion products. We use molecular dynamics simulations to show that C-59(+) and C-58(+) ions-effectively produced in prompt knockout processes with He2+-react rapidly with C-60 to form dumbbell C-119(+) and C-118(+). Ion impact on molecular clusters in general is expected to lead to efficient secondary reactions of interest for astrophysics. These reactions are different from those induced by photons.
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| 8. |
- Zettergren, Henning, et al.
(författare)
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Roadmap on dynamics of molecules and clusters in the gas phase
- 2021
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 75:5
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Tidskriftsartikel (refereegranskat)abstract
- This roadmap article highlights recent advances, challenges and future prospects in studies of the dynamics of molecules and clusters in the gas phase. It comprises nineteen contributions by scientists with leading expertise in complementary experimental and theoretical techniques to probe the dynamics on timescales spanning twenty order of magnitudes, from attoseconds to minutes and beyond, and for systems ranging in complexity from the smallest (diatomic) molecules to clusters and nanoparticles. Combining some of these techniques opens up new avenues to unravel hitherto unexplored reaction pathways and mechanisms, and to establish their significance in, e.g. radiotherapy and radiation damage on the nanoscale, astrophysics, astrochemistry and atmospheric science.
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| 9. |
- Chen, Tao, et al.
(författare)
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Formation of H2 from internally heated polycyclic aromatic hydrocarbons : Excitation energy dependence
- 2015
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 142:14
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effectiveness of molecular hydrogen (H-2) formation from Polycyclic Aromatic Hydrocarbons (PAHs) which are internally heated by collisions with keV ions. The present and earlier experimental results are analyzed in view of molecular structure calculations and a simple collision model. We estimate that H-2 formation becomes important for internal PAH temperatures exceeding about 2200 K, regardless of the PAH size and the excitation agent. This suggests that keV ions may effectively induce such reactions, while they are unlikely due to, e.g., absorption of single photons with energies below the Lyman limit. The present analysis also suggests that H-2 emission is correlated with multi-fragmentation processes, which means that the [PAH-2H](+) peak intensities in the mass spectra may not be used for estimating H-2-formation rates.
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| 10. |
- Feinberg, Alexandra J., et al.
(författare)
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X-ray diffractive imaging of highly ionized helium nanodroplets
- 2022
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Ingår i: Physical Review Research. - 2643-1564. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Finding the lowest energy configuration of N unit charges on a sphere, known as Thomson's problem, is a long-standing query which has only been studied via numerical simulations. We present its physical realization using multiply charged He nanodroplets. The charge positions are determined by x-ray coherent diffractive imaging with Xe as a contrast agent. In neutral droplets, filaments resulting from Xe atoms condensing on quantum vortices are observed. Unique to charged droplets, however, Xe clusters that condense on charges are distributed on the surface in lattice-like structures, introducing He droplets as experimental model systems for the study of Thomson's problem.
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